Geotechnical Engineering

DHARM

IDENTIFICATION AND CLASSIFICATION OF SOILS 103

Field identification

procedures (Excludingparticles larger than

80 mm

Information required for

describing soils

GW GP GM GC SW SP SM SC

Well-graded gravels,gravel-sand mixtures;little or no fines.Poorly graded gravels orgravelsand mixtures;little or no fines.Silty gravels, poorlygraded gravel-sand-siltmixturesClayey gravels, poorlygraded gravel-sand-claymixturesWell-graded sands, grav-elly sands; little or nofines.Poorly graded sands orgravelly sands; little or nofines.Silty sands, poorly gradedsand-silt-mixtures.Clayey sands, poorlygraded sand-clay mix-tures.

Wide range in grain sizesand substantial amountsof all intermediate parti-cle sizesPredominantly one size ora range of sizes with someintermediate sizes miss-ing.Non-plastic fines or fineswith low plasticity (foridentification proceduressee ML and MI below).Plastic fines (for identifi-cation procedures see CLand CI below).Wide range in grain-sizeand substantial amountsof all intermediate parti-cle sizes.Predominantly one size ora range of sizes with someintermediate sizes missing.Non-plastic fines or fineswith low plasticity (foridentification procedures,see ML and MI below).Plastic fines (for identifi-cation procedures, see CLand CI below).

Give typical name; indi-cate approximate percent-ages of sand and gravel;maximum size; anguIarity, surface condition,and hardness of the coarsegrains; local or geologicname and other pertinentdescriptive information;and symbol in parenthe-sis. For undisturbed soils andinformation on stratifica-tion; degree of compact-ness, cementation, mois-ture conditions and drain-age characteristics.Example:Silty sand, gravelly; about20% hard angular gravelparticles, 10 mm max.size; rounded and sub-an-gular sand grains; about15% non-plastic fines withlow dry strength; wellcompacted and moist; inplace; alluvial sand (SM).

Coarse grained soils

More than 50% if material larger than 75-IS Sieve. This sieve is

about the smallest particle visible to the naked eye.

Gravels Sands

More than 50% of the coarse More than 50% of the coarse

function is larger friction is smaller than

than 4.75 mm IS Sieve size 4.75 mm IS Sieve size

Clean Gravels Clean Sands

Gravels sands (with

(Little (with (Little fines)

or no fines) or no

fines) fines)

Division

Sub-

division

Group letter

symbol

Typical names

Table 4.2

Soil Classification field identification and description (IS : 1498-1970)

(Contd...)